The investigations outlined in this proposal will examine the hypothesis that during the initiation, development, and maintainace of hypertension, different mechanisms dominate at different times to elevate peripheral vascular resistance. Specifically, the goal of this proposal is to: 1) determine the sequential contribution and relative importance of neural, structural, and functional mechanisms, any of which may dominate at a different hypertension stage; 2) determine the sequential contribution and relative importance of these same mechanisms at comparable stages of hypertension (initiation, development, and maintainance) when the stimulus for the blood pressure elevation has been initiated in the juvenile compared to the adult animal. We will study these factors using a new technique, modified from Folkow's hindquarter perfusion, that allows us to determine in the same animal the relative importance of these mechanisms at any stage of hypertension. The importance of the proposed study is twofold. First, the natural history of neural, structural, and functional mechanisms in different animal models of hypertension can be determined. This will provide an insight into the similarities and contrasts between spontaneous, renovascular, and sodium-sensitive hypertension. Secondly, the influence of age on the natural history of hypertensive mechanisms can be determined. This second body of information, when combined with the first, may indicate a dominant mechanism in a select hypertension type at a specific age of onset or duration of onset. Treatment of this particular mechanism may result in improved hypertension control or delay the natural history of the disease more effectively than the use of multiple drugs, each of which has potential hazardous side-effects.